Keeping in mind that I don't know anything about Charon's orbit or gravitational effects, I think it's possible. It also doesn't have to be early in Pluto's for

Keeping in mind that I don't know anything about Charon's orbit or gravitational effects, I think it's possible. It also doesn't have to be early in Pluto's formation, either; it can be a slow, continuous, ongoing process. Salt diapirs on Earth move up through the brittle crust and 'erupt' on the surface.